1. Field of the Invention
The present invention relates to a content data storage device which uses a nonvolatile memory, like a NAND flash memory in which data is written for each page, and stores content data such as audio, and relates to a control method of the storage device.
2. Description of the Related Art
A NAND flash memory that is a nonvolatile memory is characterized by its large capacity and cheap price, then, it is widely used for a digital camera, a digital audio player, etc. NAND flash memory has a problem such as its writing rate is slow. For using the NAND flash memory in a household electronic device, this problem is not marked. However, for using the NAND flash memory to a content data storage device for broadcasting, this problem becomes marked.
As regards a conventional content data storage device, connecting a plurality of NAND flash memories in parallel has been proposed as a method of compensating for the slow rate of the writing of the NAND flash memory. However, connecting the plurality of NAND flash memories in parallel increases a page size that is a unit of writing into the NAND flash memory by the parallel number of the flash memories in comparison with the single unit of a memory IC. For instance, connecting 64 NAND flash memories of which the capacity of one page is 2,048 B (byte) in parallel increases the page size up to 131,072 B. Since audio to be used in ordinal broadcasting is 48-kHz, 16-bit stereo, a data capacity for each one second is equivalent to 192 kB/s. Since the audio data may be written in the NAND flash memory only for each page, it is needed for writing the audio data into the content data storage device in which 64 NAND flash memories are connected in parallel to accumulate the audio data of 0.638 seconds in a buffer in advance.
In recording content data by a content data storage device, it is common practice to immediately perform follow-up playback after recording and confirm whether or not the content data has been correctly recorded. However, in the aforementioned case, since the audio data may not be written in the NAND flash memory of the content data storage device after accumulating the audio data of 0.638 seconds, the follow-up playback may be performed after a lapse of 0.683 seconds. While only the case in which the delay is caused by the writing time into the NAND flash memory has described, in an actual content data storage device, since the delay is caused by other factors sometimes, the follow-up playback may not be performed after a lapse of time longer than 0.683 seconds.
In the foregoing case, while 64 NAND flash memories have been connected in parallel, for storing content data of a high-speed rate, it is needed to connect in parallel the NAND flash memories of the number higher than 64. Thereby, since the page size becomes further large, to start the follow-up playback, it must wait for a time longer than the foregoing 0.683 seconds. Increasing in length of the time until the follow-up playback starts deteriorates the operability of a series of ‘recording’ from the start of the recording up to the follow-up playback by a user.
A semiconductor memory, which automatically certify content in data register at an address within one page as a prescribed value, and can perform writing without inputting data of one page in performing writing data of a size smaller than one page when data from the prescribed address specified by an input address up to an arbitrary address is input, is proposed (for instance, refer to Jpn. Pat. Appln. KOKAI Publication 2003-178591).